This invention relates to a storage subsystem which includes a plurality of disk devices, and more particularly, to a technology of effectively using storage areas of the storage subsystem.
An example of a storage system used for a computer system is a disk array system (hereinafter, also referred to as storage subsystem) which includes a plurality of disk devices. The disk array system operates the plurality of disk devices in parallel to realize a higher speed as compared with a storage system which uses a single disk device.
A virtual volume technology has been available to efficiently use a disk capacity in the disk array system. This technology sets virtual storage areas in a computer beforehand, and allocates a physical storage area only to an area for which a write request is made among the virtual storage areas.
Another technology available to efficiently use the disk capacity is a de-duplication technology. This technology stores, when data identical to data requested to be written has been stored in the storage subsystem before reception of the write request, only a information indicating that the data is identical to the data which has been stored, but does not store the data itself requested to be written in the storage subsystem.
The de-duplication technologies are classified into a technology which executes de-duplication control for all data stored in the storage subsystem, and a technology which executes de-duplication control only for specific data registered beforehand. The former can increase a reduction effect of a storage capacity needed to store data (hereinafter, referred to as capacity reduction effect). However, processing time becomes longer, and the amount of management information increases. On the other hand, the latter can reduce management information. However, a capacity reduction effect is limited.
JP 2005-135116 A discloses a technology described below. There is provided a storage system configuring a logical storage device by dividing an area on a physical storage space formed by a group of a plurality of physical storage devices by the unit of physical block having a certain block length and by assigning the physical storage space in every physical block. This storage system includes a logical storage control table which records identification information indicating whether a physical block is assigned to data or operation is bound to data created from a predetermined data arrangement pattern in every area on the logical storage device, and a data writing unit which, upon reception of a request of writing data into an area of the logical storage device, when a data arrangement pattern of the write request matches a previously registered data arrangement pattern, records the identification information of the same data arrangement pattern into the logical storage control table correspondingly to the write request area and abandons the write request data.